This invention relates generally to fuel filters empolyed in connection with internal combustion engines. More particularly, the present invention relates to fuel filters having a replaceable cartridge for removing foreign particles and/or separating water from the fuel supply system of an internal combustion engine.
Conventionally, fuel filters employ a disposable filter cartridge which is replaced at pre-established intervals of filter usage. In practice, the filter cartridge requirements may vary depending upon such characteristics as the type and make of the internal combustion engine, the specific application for which the engine is employed, the climate in which the combustion engine is operated, and/or regional characteristics as to the quality of the fuel supply. The filter cartridges which are suitable for replacement, thus commonly vary as to axial dimensions, capacity and filter media qualities.
One of the recurring problems in assuring quality fuel filter performance is encountered in connection with replacement of the fuel cartridge. It is imperative that the replacement cartridge be compatible with the filtering requirements for the fuel system. Because for numerous types of qualities, the filter cartridge may dimensionally conform to the base of a given fuel filter assembly, replacement filter cartridges of inferior quality may not comply with the applicable specifications for a given fuel filter assembly and thereby jeopardize the integrity of the fuel filtering system. The replacement with an incompatible filter cartridge can have very serious consequences for the operation of the internal combustion engine and may also be unnecessarily more expensive than the less costly cartridges which are fully suitable. In practice, the owner of the vehicle and/or the maintenance technician servicing the internal combustion engine are frequently totally unaware of replacement filter cartridge specifications and requirements and unknowingly jeopardize the integrity of the filtering system by replacement with a wholly unsuitable cartridge even though the unsuitable cartridge at least cursorally visibly appears to be suitable. There are also, of course, instances where inferior or improper replacement filter cartridges are intentionally installed without the knowledge of the owner or the operator of the vehicle.
For many applications, it is also desirable that a cartridge be mounted to the base at a specific angular orientation so that warnings, directions and markings affixed to the cartridge may be properly positioned to ensure visibility and maximize the chances of successful information dissimination.
In U.S. patent application Ser. No. 480,032 filed on Feb. 14, 1990 and assigned to the assignee of the present invention, a key system for keying a replaceable filter cartridge to the base is disclosed. The filter system is of a type having a base with an inlet and an outlet connection with the engine fuel system and a replaceable filter cartridge mountable to the base. The replaceable cartridge includes a generally cylindrical housing which houses the fuel filter elements. At least one key projects axially from the base. A corresponding slot in the cartridge is dimensioned and located for receiving each corresponding key for locking the cartridge at a fixed angular position of the base. The keys interlock in slots of the cartridge at locations which are closely adjacent to the sealing interface of the cartridge and the sealing lip of the base.
A unique matrix of axially projecting keys is formed on each base of a given type, and a unique matrix of slots corresponding to the keys is formed in each cartridge. The key slot matrices are configured so that for a given compatible cartridge and base, the keys are interlockable in the slots to lock the cartridge at a fixed angular position of the base to thereby permit the cartridge to be securely mounted to and sealed to the base. For non-compatible cartridges and bases, the base keys are not mateable and essentially interfere with the mounting and sealing of the non-compatible cartridge so that compatible and non-compatible cartridges may be readily identified.
While the key system described in the foregoing patent application represents a significant advancement in assuring suitable fuel filter cartridge replacement, there are replacement cartridge configurations, which are closely similar in appearance to the compatible cartridges and may result in confusion and assembly difficulties. Because the key slots are not readily visible and may be similar in appearance to slots which provide for fuel communication between the cartridge and the base, it is clearly desirable that the cartridge incorporate additional keying structure which is highly visible to the maintenance technician and may also provide additional coded structural combinations to enhance the integrity and reliability of the key system.